C++: Add testcase demonstrating missing local flow out of fields that are defined by reference.

Author: MathiasVP

cpp/ql/test/library-tests/dataflow/dataflow-tests/localFlow.expected

@@ -70,3 +70,7 @@
 | test.cpp:391:11:391:13 | tmp | test.cpp:391:10:391:13 | & ... |
 | test.cpp:391:17:391:23 | source1 | test.cpp:391:10:391:13 | ref arg & ... |
 | test.cpp:391:17:391:23 | source1 | test.cpp:391:16:391:23 | & ... |
+| test.cpp:480:67:480:67 | s | test.cpp:481:21:481:21 | s |
+| test.cpp:480:67:480:67 | s | test.cpp:482:20:482:20 | s |
+| test.cpp:481:21:481:21 | s [post update] | test.cpp:482:20:482:20 | s |
+| test.cpp:482:23:482:29 | content | test.cpp:483:9:483:17 | p_content |

cpp/ql/test/library-tests/dataflow/dataflow-tests/test.cpp

@@ -470,3 +470,15 @@ void viaOutparam() {
   intOutparamSource(&x);
   sink(x); // $ ast,ir
 }
+
+void writes_to_content(void*);
+
+struct MyStruct {
+  int* content; 
+};
+
+void local_field_flow_def_by_ref_steps_with_local_flow(MyStruct * s) {
+  writes_to_content(s->content);
+  int* p_content = s->content;
+  sink(*p_content);
+}